Pindo palm

[nessa]

Just wondering what the black markings are on the spindle. I attached some pictures. 

[PindoPalm]

I also have these I just read it is a disease caused by Infected Tools, rain splatter, and human or animal contact. It can be prevented easily by sanitation.

[Merlyn]

That looks like a "petiole/rachis blight," a fungal infection.  https://edis.ifas.ufl.edu/publication/PP145

Usually it's just a cosmetic issue that affects one frond.  If it is only affecting one frond, then cutting it off near the base will help prevent it from spreading.  If it's affecting a bunch of fronds, then systemic fungicide may be a good idea.  As noted in the UFL page, picking a fungicide is kinda guesswork, as none have been really evaluated.  Banrot, Thiophanate-Methyl, Etridiazole, aluminum tris (Fosetyl-Al, Aliette, etc) are good general-purpose systemics.  Surface-based fungicides may help keep the fungus from spreading via air.  A copper-based solution, Daconil, or Mancozeb are good surface fungicides.  Copper-based ones can be phytotoxic, so should only be used once.